(A) Field of the Invention
The present invention relates to a wavelength converter structure and method for preparing the same, and more particularly, to a wavelength converter structure including at least one ridge waveguide having a periodic poled region and method for preparing the same.
(B) Description of the Related Art
Quasi-phase matching (QPM) is a technique for phase matching nonlinear optical interactions in which the relative phase is corrected at regular intervals using a structural periodicity built into the nonlinear medium, and the most popular case of interest in modern QPM technology is called frequency doubling or second harmonic generation (SHG).
U.S. Pat. No. 5,737,117 discloses, in FIG. 2b, a second harmonic generation element including a single crystal substrate having a fundamental composition of K.sub.3 Li.sub.2-2x (Nb.sub.1-y Ta.sub.y).sub.5+5z O.sub.15-x+12.5z and an optical waveguide made of an epitaxial film with a fundamental composition of K.sub.3 Li.sub.2-2a (Nb.sub.1-b Ta.sub.b).sub.5+5c O.sub.15-a+12.5c and refractive index different from that of the single crystal substrate.
U.S. Pat. No. 6,129,864 discloses a process for producing an optical waveguide substrate including a ridge-shaped structural portion containing at least an optical waveguide, which process including the steps of forming an optical waveguide-forming layer on a substrate body to prepare a substrate workpiece, and forming said ridge-shaped structural portion at said substrate workpiece by grinding.
U.S. Pat. No. 6,631,231 B2 discloses an optical waveguide element including a three-dimensional optical waveguide of a bulky non-linear optical crystal, a substrate, and a joining layer made of an amorphous material. The substrate is joined to the optical waveguide via the joining layer.
U.S. Pat. No. 7,171,094 B2 discloses an optical waveguide device including a waveguide layer that converts a wavelength of incident light and emits converted light. In the waveguide layer, a ridge waveguide and slab waveguides are provided, the slab waveguides being formed on both sides of the ridge waveguide with recess portions intervening therebetween. The waveguide layer satisfies a multi-mode condition for the incident light, and light propagating through the ridge waveguide is in a single mode.
U.S. Pat. No. 7,236,674 B2 discloses an optical waveguide device having a substrate composed of a nonlinear optical material and a periodically domain-inverted structure having the same composition as the nonlinear optical material, where the domain-inverted structure has a refractive index distribution relying on the domain-inverted structure.
US 2007/0297732 A1 discloses Optical waveguide devices characterized by low loss for a fundamental mode and high loss for higher order modes are disclosed. The high loss is sufficiently high that the waveguide is effectively single-moded.